We are requesting funds for a multiphoton laser scanning microscope system. The microscope system consists of: 1) a Zeiss 710 NLO multi-photon imaging system with 3 spectral detection channels, five laser lines for visible light excitation confocal imaging and prepared for femtosecond pulsed NIR beam;2) a Zeiss Axio Imager Z1 motorized fluorescence microscope with DIC and high resolution water immersion optics;and 3) a Coherent Chameleon free Ultrafast II Ti:Sapphire laser system. The microscope will be used to examine live small animals, organ cultures, tissue slices, whole-mount organs and isolated tissues that have been labeled with multiple parameter-indicating fluorescent probes. Two- and 3-photon imaging will minimize photo-damage and photobleaching, maximize penetration into thick specimens, permit excitation of UV-absorbing fluorophores with red and near infrared light, and optimize photon collection efficiency. The new system is sought to relieve the critically high demand for nondestructive imaging of living cells and tissues with high resolution in 3-dimensions. The multiphoton excitation microscope will provide a strong complement to our current imaging resources, which include high-resolution magnetic resonance and computerized tomography imaging. The microscope will also extend the value of a number of transgenic mouse models being studied at the Oklahoma Medical Research Foundation (OMRF). Ten major users and seven minor users will immediately employ the multiphoton microscope in fifteen independent or collaborative projects in the Programs of Arthritis and Immunology, Cardiovascular Biology, Immunobiology and Cancer, Free Radicals and Aging, and Cell, Molecular &Developmental Biology at OMRF. It is anticipated that the instrument will allow us to access novel insights in the pathological mechanisms of several diseases. A partial list of human disease studies at the OMRF that will benefit from this technology include cardiovascular and thrombotic disorders, inflammation and autoimmunity, cancer, neurodegenerative diseases and bacterial infections.